A tale of tubers & corms

Tuberophiles of the world!

This is gonna be a very short story! I seem to recall we have had this
discussion before and it is all the fault of your stupid English
language. Here in ye Olde Hollow Country we have no synonyms for these
underground storage facilities, so I don't understand the difference
between English corms and English tubers either. I suppose this goes
back to times when we were measuring in terms of "thumbs", "polluxes",
etc. Maybe if we all started to think decimal, the corm or tuber will
drop out as well.

O.k. serious: It is true, in Holland we have only one word (knol) for
what you guys call tubers/corms. The RHS dictionary of gardening says:

Corm: a solid, swollen, subterranean, bulb-like (is this to make things
easier?????) stem or stem-base; it is annual, the next year's corm
developing from the terminal bud or, in its absence, one of the lateral

Tuber: a swollen, generally subterranean stem, branch or root, used for
food storage.

Does this make any sense to anyone of you? To me these are incomparable
definitions. Let's try to match this with an Amorphophallus:

- solid: yes.
- subterranean: yes
- annual: yes, but not always (arnautovii etc.)
- bulb-like: nonsense comparison (no two bulbs are alike either).
- stem or stem-base: yes
- next year's from terminal bud etc.: yes
- food storage: yes

So, what do we have? to start with, it doesn't say whether a tuber is
annual or not. Second, both organs as described, are food (or water)
storage organs in general, so that doesn't discriminate. Ergo: these
definitions stink. 

As far as I can figure out, an amorph tuber is in fact one module out of
something that was once a number of modules. This latter pattern
suggests a stem (rhizome), which is common in aroids. Apparently in
amorphs the stem is reduced to merely one internode, upon the apex of
which develops the new internode, at the same time devouring the old
one. In many aroids we see a similar system, new internodes being built
up at the top, and old ones rotting away, but usually between the old
ones and the new ones is a series of stagnant internodes, which yields a
typical aroid "stem". This stem may be subterranean, which is then a
rhizome. This also appears in three amorphs (hayi, verticillatus and
rhizomatosus). Then we have a few amorphs that form chains of "tubers",
in which new ones develop but older ones are not immediately devoured,
yet keep their "tuberous" shape (arnautovii, pingbianensis). So, this is
the mess we deal with.

In conclusion, a "general" amorph "tuber" is ONE single internode
(module) out of a stem, and subterranean. This would come close to the
above definition of "corm", although this "annual" thing bothers me a
bit, as does "bulb-like". However, the definition of tuber mixes form
and function, which  leads to incomparable definitions. In the "corm"
definition, there is no functionality. 

The problem too is that both overlap in the use of "stem" and let's face
it, amorph "things" ARE stem(-part)s. 

So how about this one (from Lawrence 1955 Taxonomy of vascular plants):

Corm: a solid, bulb-like part of the stem, usually subterranean, as the
"bulb" of Crocus and Gladiolus.

Tuber: a short, congested part; usually defined as subterranean (as of a
rootstock) although this is not essential.

Does this help? If we take "bulb-like" literally, then we HAVE to assume
that a corm has scale-like organs, which may or may not be homologous to
the scales of a true bulb (which are modified leaves). Phalloid "things"
don't have scales in that sense and that would rule out "corms" then.
The Lawrence definition of tuber is SO simple that it fits (but it may
fit just about any congested part of a plant). 

When I have checked out Stearn, Botanical Latin, i'll be


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